This is a list of Hypertext Transfer Protocol (HTTP) response status codes. It includes codes from IETF Request for Comments (RFCs), other specifications, and some additional codes used in some common applications of the Hypertext Transfer Protocol (HTTP). The first digit of the status code specifies one of five standard classes of responses. The message phrases shown are typical, but any human-readable alternative may be provided. Unless otherwise stated, the status code is part of the HTTP/1.1 standard (RFC 7231).[1]

Microsoft Internet Information Services (IIS) sometimes uses additional decimal sub-codes for more specific information,[3] however these sub-codes only appear in the response payload and in documentation, not in the place of an actual HTTP status code.

An informational response indicates that the request was received and understood. It is issued on a provisional basis while request processing continues. It alerts the client to wait for a final response. The message consists only of the status line and optional header fields, and is terminated by an empty line. As the HTTP/1.0 standard did not define any 1xx status codes, servers must not[note 1] send a 1xx response to an HTTP/1.0 compliant client except under experimental conditions.[4]

100 Continue

The server has received the request headers and the client should proceed to send the request body (in the case of a request for which a body needs to be sent; for example, a POST request). Sending a large request body to a server after a request has been rejected for inappropriate headers would be inefficient. To have a server check the request's headers, a client must send Expect: 100-continue as a header in its initial request and receive a 100 Continue status code in response before sending the body. The response 417 Expectation Failed indicates the request should not be continued.[2]

101 Switching Protocols

The requester has asked the server to switch protocols and the server has agreed to do so.[5]

A WebDAV request may contain many sub-requests involving file operations, requiring a long time to complete the request. This code indicates that the server has received and is processing the request, but no response is available yet.[6] This prevents the client from timing out and assuming the request was lost.

This class of status codes indicates the action requested by the client was received, understood, accepted, and processed successfully.[2]

200 OK

Standard response for successful HTTP requests. The actual response will depend on the request method used. In a GET request, the response will contain an entity corresponding to the requested resource. In a POST request, the response will contain an entity describing or containing the result of the action.[7]

201 Created

The request has been fulfilled, resulting in the creation of a new resource.[8]

202 Accepted

The request has been accepted for processing, but the processing has not been completed. The request might or might not be eventually acted upon, and may be disallowed when processing occurs.[9]

203 Non-Authoritative Information (since HTTP/1.1)

The server is a transforming proxy (e.g. a Web accelerator) that received a 200 OK from its origin, but is returning a modified version of the origin's response.[10][11]

204 No Content

The server successfully processed the request and is not returning any content.[12]

205 Reset Content

The server successfully processed the request, but is not returning any content. Unlike a 204 response, this response requires that the requester reset the document view.[13]

The server is delivering only part of the resource (byte serving) due to a range header sent by the client. The range header is used by HTTP clients to enable resuming of interrupted downloads, or split a download into multiple simultaneous streams.[14]

This class of status code indicates the client must take additional action to complete the request. Many of these status codes are used in URL redirection.[2]

A user agent may carry out the additional action with no user interaction only if the method used in the second request is GET or HEAD. A user agent may automatically redirect a request. A user agent should detect and intervene to prevent cyclical redirects.[17]

This is an example of industry practice contradicting the standard. The HTTP/1.0 specification (RFC 1945) required the client to perform a temporary redirect (the original describing phrase was "Moved Temporarily"),[20] but popular browsers implemented 302 with the functionality of a 303 See Other. Therefore, HTTP/1.1 added status codes 303 and 307 to distinguish between the two behaviours.[21] However, some Web applications and frameworks use the 302 status code as if it were the 303.[22]

The response to the request can be found under another URI using a GET method. When received in response to a POST (or PUT/DELETE), the client should presume that the server has received the data and should issue a redirect with a separate GET message.[23]

Indicates that the resource has not been modified since the version specified by the request headers If-Modified-Since or If-None-Match. In such case, there is no need to retransmit the resource since the client still has a previously-downloaded copy.[24]

305 Use Proxy (since HTTP/1.1)

The requested resource is available only through a proxy, the address for which is provided in the response. Many HTTP clients (such as Mozilla[25] and Internet Explorer) do not correctly handle responses with this status code, primarily for security reasons.[26]

306 Switch Proxy

No longer used. Originally meant "Subsequent requests should use the specified proxy."[27]

307 Temporary Redirect (since HTTP/1.1)

In this case, the request should be repeated with another URI; however, future requests should still use the original URI. In contrast to how 302 was historically implemented, the request method is not allowed to be changed when reissuing the original request. For example, a POST request should be repeated using another POST request.[28]

The request and all future requests should be repeated using another URI. 307 and 308 parallel the behaviors of 302 and 301, but do not allow the HTTP method to change. So, for example, submitting a form to a permanently redirected resource may continue smoothly.[29]

This class of status code is intended for situations in which the error seems to have been caused by the client. Except when responding to a HEAD request, the server should include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition. These status codes are applicable to any request method. User agents should display any included entity to the user.[30]

400 Bad Request

The server cannot or will not process the request due to an apparent client error (e.g., malformed request syntax, size too large, invalid request message framing, or deceptive request routing).[31]

Similar to 403 Forbidden, but specifically for use when authentication is required and has failed or has not yet been provided. The response must include a WWW-Authenticate header field containing a challenge applicable to the requested resource. See Basic access authentication and Digest access authentication.[32] 401 semantically means "unauthenticated",[33] i.e. the user does not have the necessary credentials.

Note: Some sites issue HTTP 401 when an IP address is banned from the website (usually the website domain) and that specific address is refused permission to access a website.

402 Payment Required

Reserved for future use. The original intention was that this code might be used as part of some form of digital cash or micropayment scheme, as proposed for example by GNU Taler[34], but that has not yet happened, and this code is not usually used. Google Developers API uses this status if a particular developer has exceeded the daily limit on requests.[35]

The server timed out waiting for the request. According to HTTP specifications: "The client did not produce a request within the time that the server was prepared to wait. The client MAY repeat the request without modifications at any later time."[38]

409 Conflict

Indicates that the request could not be processed because of conflict in the request, such as an edit conflict between multiple simultaneous updates.

410 Gone

Indicates that the resource requested is no longer available and will not be available again. This should be used when a resource has been intentionally removed and the resource should be purged. Upon receiving a 410 status code, the client should not request the resource in the future. Clients such as search engines should remove the resource from their indices.[39] Most use cases do not require clients and search engines to purge the resource, and a "404 Not Found" may be used instead.

411 Length Required

The request did not specify the length of its content, which is required by the requested resource.[40]

The URI provided was too long for the server to process. Often the result of too much data being encoded as a query-string of a GET request, in which case it should be converted to a POST request.[43] Called "Request-URI Too Long" previously.[44]

415 Unsupported Media Type

The request entity has a media type which the server or resource does not support. For example, the client uploads an image as image/svg+xml, but the server requires that images use a different format.

The client has asked for a portion of the file (byte serving), but the server cannot supply that portion. For example, if the client asked for a part of the file that lies beyond the end of the file.[45] Called "Requested Range Not Satisfiable" previously.[46]

417 Expectation Failed

The server cannot meet the requirements of the Expect request-header field.[47]

The origin server requires the request to be conditional. Intended to prevent the 'lost update' problem, where a client GETs a resource's state, modifies it, and PUTs it back to the server, when meanwhile a third party has modified the state on the server, leading to a conflict."[53]

A server operator has received a legal demand to deny access to a resource or to a set of resources that includes the requested resource.[54] The code 451 was chosen as a reference to the novel Fahrenheit 451.

Response status codes beginning with the digit "5" indicate cases in which the server is aware that it has encountered an error or is otherwise incapable of performing the request. Except when responding to a HEAD request, the server should include an entity containing an explanation of the error situation, and indicate whether it is a temporary or permanent condition. Likewise, user agents should display any included entity to the user. These response codes are applicable to any request method.[56]

500 Internal Server Error

A generic error message, given when an unexpected condition was encountered and no more specific message is suitable.[57]

501 Not Implemented

The server either does not recognize the request method, or it lacks the ability to fulfil the request. Usually this implies future availability (e.g., a new feature of a web-service API).[58]

502 Bad Gateway

The server was acting as a gateway or proxy and received an invalid response from the upstream server.[59][60]

503 Service Unavailable

The server is currently unavailable (because it is overloaded or down for maintenance). Generally, this is a temporary state.[61]

504 Gateway Timeout

The server was acting as a gateway or proxy and did not receive a timely response from the upstream server.[62]

505 HTTP Version Not Supported

The server does not support the HTTP protocol version used in the request.[63]

The client needs to authenticate to gain network access. Intended for use by intercepting proxies used to control access to the network (e.g., "captive portals" used to require agreement to Terms of Service before granting full Internet access via a Wi-Fi hotspot).[53]

The server cannot honour the request because the user has not provided the required information.[77]

451 Redirect

Used in Exchange ActiveSync when either a more efficient server is available or the server cannot access the users' mailbox.[78] The client is expected to re-run the HTTP AutoDiscover operation to find a more appropriate server.[79]